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62 Cards in this Set
- Front
- Back
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English language has how many letters |
26 |
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Computer language (binary system) has how many letters |
2 (1&0) |
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Each binary number represents an |
Electrical current being either off or on |
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Each binary number is stored as a |
Binary digit or bit |
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How many bits make up a letter of the English alphabet |
8 |
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8 bits= |
1 byte |
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Storage ability is stated in # of |
Bytes (10 gigabytes, 100 megabytes) gigs = 1 billion |
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Images are displayed in a |
Matrix ( rows and column of the same size boxes) |
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Each box surface is called a |
Picture element or pixel (3d imaging uses a voxel) |
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Each pixel is assigned a |
Number |
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Numbers represent a specific shade of |
Gray |
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How many shades of gray per box |
1 |
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Matrix dimensions are |
Constant |
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The more __ in any matrix, the __ each box, and the __ numerical values can be assigned |
Pixels, smaller, more ( better reproduction of image and spacial resolution) |
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What is gray scale bit depth |
How many shades of gray are available to each pixel |
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The more __ in a pixel, the __ shades of gray it's capable of displaying |
Bits, more |
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What is the bit range |
8-32 |
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More bits have a better __ capabilities |
Storage |
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What is dynamic range and density resolution |
Number of shades of gray an image system can show |
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More bits the greater the density __ |
Resolution |
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The more bits the large the dynamic __ |
Range |
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Trade off the more bits means slower __ and more __ __ required |
Processing, storage space |
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What does the stored histogram represent |
An ideal image for each body part |
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What is calculated from an exposure made from the correct exposure factors |
Histogram |
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What does the computer see to process the image |
Data values from the histogram |
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Pixels are sorted by the amount of __ they receive |
Exposure |
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What does the computer do with the number of pixels at each exposure value that are added up |
It graphs them |
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What does the histogram represent |
How much exposure the IR receives |
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What is the vertical axis of the histogram |
# of pixels |
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What does the horizontal axis of the histogram represent |
How much exposure |
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Your histogram is compared to the ideal or |
Reference histogram |
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What are the two things that happen when processing your histogram |
Your histogram is adjusted to line up with the computers ideal(called shifting it rescaling) (density is altered), exposure index # is calculated to tell you if your image was under, over, or correctly expose |
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A wide histogram demonstrates higher |
Contrast (black to white) |
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A narrow histogram demonstrate less |
Contrast (small changes in color) |
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What is identified when you take an image |
A histogram of your image is created, and the VOI(value of interest) is identified (useful data) |
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What is the histogram actually representing |
The exposure |
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What does LUT represent |
Look up tables |
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What does the LUT do |
Adjust the image for optimal contrast, or imaging would always show low contrast |
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Is there a optimal LUT for each body part |
Yes, this is why you must choose the correct body part when imaging |
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What is modifying the brightness and contrast on the monitor called |
Windowing |
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How many shades of gray can the human visual system detect |
32 |
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How many shades of gray can the computer show |
Over 1000 |
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What will change the numeric value of each displaying pixel |
Window width and leveling |
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Range of densities to be displayed |
Window width |
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Large or wide width have __ subtle shades of gray to choose from |
Many (low contrast image) |
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Small or narrow width __ shades of gray to choose from |
Few (high contest image) |
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Controls image brightness/density |
Window level (picks center value of the width range) |
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Window width controls |
Contrast |
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Window level controls |
Brightness |
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Techs may limit how much a radiologist can adjust the image by |
Setting a narrow width, or an extreme level, fix this by talking to a friendly radiologist |
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What allows great latitude in digital imaging |
Histogram and LUT |
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What helps determine if the correct exposure parameters were used |
Exposure index number |
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Numbers indicate how much exposure reached the IR, will let you know if the system thinks you correctly exposed, under, over exposed the image |
Exposure index number |
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What is the range of exposure |
0.1-100mR |
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Can use this to better practice ALARA, can be used in quality control and radiation protection |
Exposure index |
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What are some manufacture differences for defining EI number |
Beam quality outputs, receptor sensitivity, software interpretation |
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Exposure index system.. Some directly relate to __ of inversely relate to |
Dose |
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What is spacial resolution determined by |
Pixel size, smaller the pixel size the better |
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What are the two categories of noise |
Electronic system noise, quantum mottle noise |
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What is SNR and CNR |
Signal to noise ratio, contrast to noise ratio, high SNR a lot of signal and not much noise |
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DQE |
Detective quantum efficiency, how accurately did the IR convert the incoming data to the output screen, perfect system DQE of 1 |
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Are there any perfect DQE systems |
No, range is 0.3-0.7, 30-70% |
